This grant application is aimed to obtain support for our institution's activities in the Pediatric Oncology Group (POG). We applied for POG membership in January 1981 and were accepted at the March 1981 meeting in St. Louis. By December 31, 1981, our institution had already registered 31 patients on group protocols and several of its investigators had become members of key committees and coordinators of major protocols. We now propose a major commitment of resources to Pediatric Oncology Group research studies. This grant proposal describes the personnel and facilities in our institution and its affiliated hospitals with which we aim to carry out Pediatric Oncology Group related research activities. The recent past history of active participation in clinical cancer research and our initial contribution to Pediatric Oncology Group functions provides evidence of our commitment. Specifically, we aim to participate in Pediatric Oncology Group research studies by: 1) actively enrolling as many as possible of our 60-80 new pediatric patients with cancer each year on Pediatric Oncology Group treatment and ancillary protocols; 2) collecting, recording, and submitting all necessary data in a timely and organized fashion in order that our protocol entries are completely eligible for anlaysis; 3) making scientific contributions to the Pediatric Oncology Group by actively serving on committees and as protocol coordinators; 4) participating as a reference laboratory for the entire Pediatric Oncology Group for studies aimed at detecting minimal residual disease and early prediction of relapse in patients with acute lymphoblastic leukemia in second remission. The studies will explore terminal deoxynucleotidyl transferase and other markers to identify leukemia cells in the peripheral blood of these patients.